Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint=true, so the description need not restate safety. It adds useful behavioral context: the index is updated daily, it uses stochastic optimization over specified data feeds, and it returns trend/confidence/top_drivers in addition to the score. This goes beyond the annotation without contradicting it.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Three sentences: first states purpose and output, second gives explicit when-to-use, third states update frequency. Every sentence earns its place with no fluff or repetition. Front-loaded with the most important information.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

The tool is moderately complex (stochastic index with multiple inputs and outputs), and the description covers what it returns, when to use it, and its update cadence. Since there is no output schema, the explicit listing of score, trend, confidence, and top_drivers fills that gap. The parameter is simple and well-documented. This is complete for an agent to select and invoke it correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100% for the only parameter 'days', which has a detailed description in the schema including the Gold tier caveat. The tool description does not add semantic detail about the parameter, but per the rubric, a high coverage baseline of 3 applies. No extra credit needed.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool returns a 0-100 supply-chain disruption cost index, with specific methodology (stochastic optimization over lead-time volatility, demand variance, holding costs) and output components (score, trend, confidence, top_drivers). This is a specific verb+resource+scope that distinguishes it from the many opaque sibling tools.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description explicitly says when to call: 'when the user asks about supply-chain disruption, stockout risk, or freight cost pressure, or when timing a hedge-now versus wait inventory decision.' This gives clear context, though it does not mention alternatives or when-not-to-use, so it stops short of a 5.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.